Optical arrangements for head mounted displays

ABSTRACT

A mechanism for adjusting an apparatus for the inter-pupilar distance of a user is disclosed. Example embodiments of the disclosed mechanism use gears that link the movements of eye-optics and reflectors placed along the optical path. When the eye-optics are adjusted, this movement causes a movement in the linked reflectors that maintains a constant length for the optical path.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is related to concurrently filed, co-pending,and commonly assigned U.S. patent application Ser. No. ______, [AttorneyDocket No. 54729-P005US-10304870], entitled “MULTIPLE IMAGINGARRANGEMENTS FOR HEAD MOUNTED DISPLAYS,” the disclosure of which ishereby incorporated herein by reference.

PRIORITY

The present application claims priority to Hungarian Patent Application,Serial No. P 02 03993, Filed, Nov. 19, 2002, entitled “OPTICAL SYSTEMFOR A BINOCULAR VIDEO SPECTACLE,” the disclosure of which is herebyincorporated herein by reference.

TECHNICAL FIELD

The invention relates generally to visual displays and more specificallyto optical arrangements for head mounted systems that use a singledisplay.

BACKGROUND OF THE INVENTION

Head Mounted Displays (HMDs) are a class of image display devices thatcan be used to display images from television, digital versatile discs(DVDs), computer applications, game consoles, or other similarapplications. A HMD can be monocular ( a single image viewed by oneeye), biocular (a single image viewed by both eyes), or binocular (adifferent image viewed by each eye). Further, the image projected to theeye(s) may be viewed by the user as complete, or as superimposed on theuser's view of the outside world. HMD designs must account forparameters such as image resolution, the distance of the virtual imagefrom the eye, the size of the virtual image (or the angle of the virtualimage), the distortions of the virtual image, the distance between theleft and the right pupil of the user (inter pupillar distance (IPD)),diopter correction, loss of light from image splitting and transmission,power consumption, weight, and price. Ideally, a single HMD wouldaccount for these parameters over a variety of users and be able todisplay an image regardless of whether it was a stereo binocular imageor a simple monoscopic image.

If the resolution of a picture on the HMD's internal display is 800×600pixels, an acceptable size for the virtual image produced by the HMD'soptics is a virtual image diameter of approximately 1.5 m (52″-56″) at 2m distance which corresponds to approximately a 36° angle of view. Toproperly conform to the human head and eyes, the IPD should be variablebetween 45 mm and 75 mm. In order to compensate for near- andfarsightedness, at least a ±3 diopter correction is necessary.

The use of only one microdisplay in the HMD (instead of using one foreach eye) drastically reduces the price of the device. Typically, anarrangement for such a unit positions a microdisplay between the user'seyes. The image produced is then split, enlarged, and separatelytransmitted to each eye. There are numerous designs known in the art forbeam splitting in single display HMDs with a center mounted display, butnone are known that provide a solution that is cheap, light weight,small in size, and capable of displaying all varieties of images.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the present invention reduce the splitting volume of headmounted displays by focusing the image produced by a single displayscreen and splitting that image near its focal point. The separatesub-images are then focused and propagated through a plurality ofoptical sub-paths delivering the image to separate locations.

Some embodiments utilize an asymmetrical V-mirror splitter which canconsist of a partially reflective surface and a fully reflective surfaceplaced near the focal point of the image. A portion of the lightcontaining the image information is then reflected by the partiallyreflective surface and can be channeled to one eye, while the remainingportion of the light is reflected by the fully reflective surface andchanneled to the other eye.

Some embodiments may also utilize diffusers onto which real images ofthe display are formed. Real images are projected onto diffusers bytransition optics having a small numerical aperture, and transmitted toa viewer's eyes by optics having a larger numerical aperture.

Some embodiments may also utilize rotating reflectors. By reflecting thesplit images off of multiple reflectors, the path of these images can bealtered in a manner that allows the embodiments to adjust for the interpupillar distances of different users. Other embodiments utilize thesynchronized movement of multiple optical blocks to adjust for theinterpupillary distance of different users.

Further embodiments may also utilize a light source to illuminate thedisplay. One possible arrangement may include individual sources ofnarrow wavelength light arranged to approximate a single wide bandsource.

The foregoing has outlined rather broadly the features and technicaladvantages of the present invention in order that the detaileddescription of the invention that follows may be better understood.Additional features and advantages of the invention will be describedhereinafter which form the subject of the claims of the invention. Itshould be appreciated that the conception and specific embodimentdisclosed may be readily utilized as a basis for modifying or designingother structures for carrying out the same purposes of the presentinvention. It should also be realized that such equivalent constructionsdo not depart from the invention as set forth in the appended claims.The novel features which are believed to be characteristic of theinvention, both as to its organization and method of operation, togetherwith further objects and advantages will be better understood from thefollowing description when considered in connection with theaccompanying figures. It is to be expressly understood, however, thateach of the figures is provided for the purpose of illustration anddescription only and is not intended as a definition of the limits ofthe present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, reference isnow made to the following descriptions taken in conjunction with theaccompanying drawing, in which:

FIG. 1 illustrates a top view of a head mounted display arrangedaccording to an embodiment of the present invention;

FIG. 2 illustrates a prospective view of a head mounted display arrangedaccording to an embodiment of the present invention;

FIG. 3 illustrates a prospective view of a head mounted display arrangedaccording to an embodiment the present invention;

FIGS. 4A and 4B illustrate a prospective view of a head mounted displayarranged according to an embodiment of the present invention;

FIGS. 5A and 5B illustrate a prospective view of a head mounted displayarranged according to an embodiment of the present invention;

FIG. 6 illustrates a top view of a portion of a head mounted displayarranged according to an embodiment of the present invention;

FIG. 7 illustrates a top view of a portion of a head mounted displayarranged according to an embodiment of the present invention;

FIG. 8 illustrates a top view of a portion of a head mounted displayarranged according to an embodiment of the present invention; and

FIG. 9 illustrates a top view of a portion of a head mounted displayarranged according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a top view of head mounted device 100 arrangedaccording to an embodiment of the present invention. Sub-image creationsection 101, within device 100, creates a plurality of sub-images from asingle image source into a plurality of optical sub-paths. Display 110can be any suitable apparatus or screen operable to display a visualimage of data, such as a liquid crystal display (LCD) screen. Display110 is situated along a display axis 111, which, in the embodimentshown, is normal to the screen of display 110 and perpendicular tofacial plane 170 of a user. Display 110 is designed to project a displayimage along optical path 112. In the arrangement of section 101, opticalpath 112 lies along display axis 111. Display lens 115 is located along,and perpendicular to, optical path 112, and has display lens focal point124. Display lens focal point 124 lies on optical path 112, and section101 is arranged such that display lens focal point 124 lies withinsplitter 120. By focusing the display image before it is split, thesplitting of volume of sub-image creation section 101 can be greatlyreduced. A small splitting volume allows an embodiment to use small,light-weight splitting elements and allows HMD designs to includeadvantageous arrangements and additional optical elements that improveimage quality and can increase the size of the image viewed by a user.The embodiment of FIG. 1 is arranged to produce an image through(approximately) collimated light emanated by (or being reflected from)display 110, thus splitter 120 is placed proximate to display lens focalpoint 124. The embodiments are not limited to this arrangement however,as splitter 120 should be arranged in the position most appropriate tothe focused image. For example, if display 110 emits, transmits, orreflects non collimated light, the display image will be focused to a“point” that is not display lens focal point 124, and embodiments willarrange splitter 120 in a position proximate to this focal area.

In embodiments using the arrangement of section 101, splitter 120 is anasymmetric V-mirror splitter composed of a partially reflective surface121 and a fully reflective surface 122. The proximity of surfaces 121,122 will be dependent upon the size of splitter 120 and the amount ofsplitter volume reduction section 101 is arranged to produce. Section101 is further arranged so that surface 121 and surface 122 share acommon edge, and are arranged asymmetrically about display axis 111.Section 101 can thus split a display image of display 110 into twoseparate display sub-images. The term sub-image is used to describe themultiple images of a display created by the various embodiments of thepresent invention. The sub-images of FIG. 1 contain all of theinformation of a display, but embodiments may use sub-images thatcontain only a portion of an image.

Upon striking partially reflective surface 121, a portion of a displayimage is reflected along left-eye optical sub-path 140, and becomes aleft-eye sub-image. The portion of a display image not reflected bypartially reflective surface 121 passes through and strikes fullyreflective surface 122, becoming a right-eye sub-image, which isreflected along right-eye optical sub-path 130. The result is anidentical left-eye sub-image and right-eye sub-image traveling inopposite directions and containing identical image information.

Left-eye sub-image will follow optical sub-path 140 and be channeled toleft eye 146 of a user. Placed along optical sub-path 140 is left-eyereflector 142, which is a fully reflective surface arranged to redirectleft-eye optical sub-path 140 by 90° and into left eyepiece optics 145.The right-eye sub-image will follow optical sub-path 130 and bechanneled to right eye 136 of a user. Placed along optical sub-path 130is right-eye reflector 132, which is a fully reflective surface arrangedto redirect right-eye optical sub-path 130 by 90° and into righteyepiece optics 135. Right eyepiece optics 135 and left eyepiece optics145 can be a single lens or a combination of several lenses designed toappropriately magnify a right-eye sub-image for viewing by right eye 136of the user and a left-eye sub-image for viewing by left eye 146 of theuser, respectively.

Eyepiece optics 135 and 145 are adjustable single lenses, but otherembodiments may use multiple lenses or any other arrangement thatappropriately focuses a right-eye sub-image and a left-eye sub-image forviewing by right eye 136 and left eye 146, respectively. Further,although reflectors 142, 132 of device 100 are depicted as mirrors,embodiments are not limited to the use of mirrors for redirecting anoptical sub-path. Rather, prisms, partially reflective surfaces,polarizing beam splitters, or any other suitable arrangements can beused for redirecting an optical sub-path.

Device 100 is also capable of adjusting for the varying IPDs ofdifferent users through the synchronized movements of optical elements.Right eyepiece optics 135 and left eyepiece optics 145 can shift throughmovements 152 and 151 respectively to create IPD 150 a and IPD 150 b,when section 101 shifts through movement 155. When IPD distance 150 a ischanged to IPD 150 b, section 101 is simultaneously shifted towardfacial plane 170 in movement 155 (downwards in the view of FIG. 1). WhenIPD 150 b is changed to 150 a, section 101 is simultaneously shiftedaway from plane 170 (upwards in the view of FIG. 1). These synchronizedmovements allow device 100 to adjust to accommodate for the entire rangebetween IPD 150 a and 150 b while maintaining constant distances betweensurfaces 122, 121 and eyepiece optics 135, 145 along sub-paths 130 and140, respectively. Device 100 is also capable of diopter correctionthrough additional adjustments of movement 153 of left eyepiece optics145 and movement 154 of right eyepiece optics 135.

FIG. 2 illustrates a prospective view of head mounted device 200arranged according to an embodiment of the present invention. Headmounted device 200 includes section 101, as described in relation toFIG. 1, which operates to split a display image of display 110 into aleft-eye sub-image traveling along left-eye optical sub-path 140 and aright-eye sub-image traveling along right-eye optical sub-path 130. Fordevice 200, left-eye transition optics 243 are placed along left-eyeoptical sub-path 140 to adjust the left-eye sub-image for reflection byleft-eye reflector 142 onto left-eye diffuser 244. The left-eyesub-image strikes the left-eye diffuser 244 and creates a real image ofthe display on the diffuser surface. The left eyepiece compound optics245 then magnifies this real image appropriately for left eye 146.

The embodiment depicted in FIG. 2 is described using diffusers ontowhich real images are projected in order to prepare the image.Transition optics, having a small numerical aperture, project a realimage onto the diffuser surface, and eyepiece optics having a largenumerical aperture transport the image to the eyes of a user. Rather,any appropriate means may be used including microlens arrays,diffraction gratings, or other diffractive surfaces. For the purposes ofthe present invention, it will be understood that “diffuser” as used todescribe the embodiments of the present invention, refers to all suchmeans used to convert incident angular power density into an appropriateexiting angular power density.

In FIG. 2, a right-eye sub-image follows the right-eye optical sub-path130 into right eye transition optics 233. The right eye transitionoptics 233 adjusts the right-eye display sub-image appropriately forreflection by right-eye reflector 132 onto right-eye diffuser 234. Theright-eye sub-image strikes right-eye diffuser 234 and creates a realimage. This real image is adjusted by right eyepiece compound optics 235appropriately for right eye 136. Device 200 is capable of dioptercorrection through movement 253 of left-eye compound optics 245 and ofmovement 254 of right-eye compound optics 235.

Device 200 is also capable of IPD adjustment through multiplesynchronous movements. IPD 150 can be shortened by shifting left-eyecompound optics 234 to the right with movement 251, and right-eyecompound optics 235 to the left with movement 252. For the embodiment ofFIG. 2, segment 240 of optical sub-path 140 lies between transitionoptics 243 and diffuser 244, and segment 230 of optical sub-path 130lies between transition optics 233 and diffuser 234. Thus, as compoundoptics 235 and 245 are shifted in movement 252 and 251 to shortendistance 150, center section 201 should be shifted away from the facialplane 170. The embodiment of FIG. 2 describes one combination ofsynchronous movements that result in IPD adjustment, but embodiments ofthe present invention are not limited to the synchronous movements ofFIG. 2.

FIG. 3 illustrates a prospective view of a head mounted device arrangedaccording to an embodiment of the present invention. Head mounted device300 includes section 101, as described in relation to FIG. 1, to split adisplay image of display 110 into a left-eye sub-image traveling alongleft-eye optical sub-path 140 and a right-eye sub-image traveling alongright-eye optical sub-path 130. In the embodiment depicted in FIG. 3, aleft-eye display sub-image follows left-eye optical sub-path 140 andpasses through a left-eye real image reflector 342 to strike left-eyereflective diffuser 343, thus creating a real image. This real image isthen reflected by left-eye real image reflector 342 into left eyepieceoptics 145. Left eyepiece optics 145 adjusts a reflected real imageappropriately for left-eye 146. A right-eye display sub-image willfollow right-eye optical sub-path 130 passing through right-eyereal-image reflector 332 to strike right-eye reflective diffuser 333,thus creating a real image. This real image is reflected by right-eyereal-image reflector 332 into right eyepiece optics 135 which willadjust a reflected real-image appropriately for right-eye 136.

The embodiment depicted in FIG. 3 is described as using reflectivediffusers on which real images are formed. The present invention is notlimited to the use of any one type of diffuser. Rather, the embodimentsmay use any appropriate diffuser, as previously described, and may beany appropriate shape such as spherical, flat, or aspheric.

The embodiment in FIG. 3 is also capable of diopter correction throughmovement 153 of left eyepiece optics 145 and movement 154 of righteyepiece optics 135. Left-eye real-image reflector 342 and left eyepieceoptics 145 collectively make up left eyepiece 360. Right-eye real-imagereflector 332 and right eyepiece optics 135 collectively make up righteyepiece 361.

Device 300 is capable of IPD adjustment through multiple simultaneousmovements. The embodiment of FIG. 3 simultaneously moves left eyepiece360 and right eyepiece 361 through movements 351 and 352 respectively toset the correct IPD. At the same time, movement 153 of left eyepieceoptics 145 and movement 154 of right eyepiece optics 135 are moved tomaintain the optical path lengths between eyepiece optics 145, 135 andreflective diffusers 343, 333.

In device 300, left-eye real-image reflector 342 and right-eyereal-image reflector 332 are partially reflective surfaces, butembodiments are not limited to the arrangement depicted. Rather,embodiments may easily be adapted to any arrangement, such as thoseusing prisms, or polarizing beam splitters, that appropriately reflectlight into eyepiece optics 135 and 145 and transmit light from opticalpaths 130, 140 towards reflective diffusers 333, 343, respectively.

FIGS. 4A and 4B illustrate a prospective view of head mounted device 400arranged according to an embodiment of the present invention. Headmounted device 400 uses right angle sub-image creation section 401 tocreate a plurality of display sub-images from a single image source.Similar to section 101 described in FIGS. 1-3, section 401 splits adisplay image of display 110 into left-eye sub-image traveling alongleft-eye optical sub-path 140 and a right-eye sub-image traveling alongright-eye optical sub-path 130. In section 401, display 110 and displayoptics 115 are rotated 90° from section 101 of FIGS. 1 through 3.Display 110 projects a display image along optical path 112 where it isfocused by display optics 115. A display image then strikes displayreflector 416, which redirects the optical path 112 by 90°. Reflector416 causes a focused display image to be directed into splitter 120. Byredirecting the optical path with reflector 416, the total volume ofsection 401 is reduced. The volume may be further reduced by addingadditional similar reflectors. In section 401, splitter 120 is arrangedsuch that partially reflective surface 121 and fully reflective surface122 are parallel to display axis 111, and reflected focal point 424 ofthe display optics 115 lies inside of splitter 120. Partially reflectivesurface 121 reflects a portion of a display image as a left-eye displaysub-image to follow left-eye optical sub-path 140 such that it strikesleft-eye reflector 142. The portion of the display image not reflectedby partially reflective surface 121 is reflected by fully reflectivesurface 122 as a right-eye sub-image along right-eye optical sub-path130 such that it strikes right-eye reflector 132.

Device 400 uses “real” images in a manner similar to device 200 of FIG.2. For device 400, a left-eye display sub-image is reflected to left-eyediffuser 243, where a real image is created. This real image is thentransported to left-eye 146 by left eyepiece optics 145, which isdesigned to appropriately focus a left-eye sub-image for viewing byleft-eye 146. A right-eye display sub-image will be reflected ontoright-eye diffuser 234 creating a real image, which is transported toright-eye 136 by right eyepiece optics 135, which is designed toappropriately focus a right-eye sub-image for viewing by right-eye 136.Device 400 is capable of diopter correction through movement 153 of lefteyepiece optics 145 and movement 154 of right eyepiece optics 135.

FIG. 4B illustrates the IPD correction capability of device 400. In thisembodiment, fully reflective surface 122 and partially reflectivesurface 121 are rotatable about splitter axis 423 and with respect toeach other. When fully reflective surface 122 is rotated clockwise aboutaxis 423 and partially reflective surface 121 is rotatedcounter-clockwise, right-eye optical sub-path 130 and left-eye opticalsub-path 140 are deflected out of the plane, and are no longer 180° fromeach other. When right-eye optical sub-path 130 and left-eye opticalsub-path 140 are deflected some angles theta (θ) and theta prime (θ′),the result is that device 400 has adjusted IPD 450. Eyepieces 460 and461 rotate inward simultaneously with the rotation of surfaces 121, 122.Eyepiece 460 rotates counterclockwise to follow the downward deflectionof sub-path 140, and eyepiece 461 rotates clockwise to follow thedownward deflection of sub-path 130. These simultaneous rotations resultin adjusted IPD 450.

FIGS. 5A and 5B illustrate a prospective view of a head mounted display500 arranged according to an embodiment of the present invention. Forhead mounted device 500, section 101 is again used to split the displayimage of display 110 into a left-eye sub-image traveling along left-eyeoptical sub-path 140 and a right-eye sub-image traveling along right-eyeoptical sub-path 130. For display 500, a left-eye display sub-image willstrike a left-eye reflector 142 causing left-eye optical sub-path 140 tobe redirected 90°. A left-eye display sub-image will then strike secondleft-eye reflector 543, which also causes left-eye optical sub-path 140to be redirected 90°. Left-eye reflector 142 and second left-eyereflector 543 are arranged along a common left-eye reflector axis 541.Once a left-eye display sub-image has been reflected by the secondleft-eye reflector 543, it is reflected by third left left-eye reflector544 and redirected onto left-eye diffuser 243.

Similarly, a right-eye display sub-image will strike a right-eyereflector 132 causing right-eye optical sub-path 130 to be redirected90°. A right-eye display sub-image will then strike second right-eyereflector 533, which also causes right-eye optical sub-path 130 to beredirected 90°. Right-eye reflector 132 and second right-eye reflectors533 are arranged along a common right-eye reflector axis 531. Once aright-eye display sub-image has been reflected by second right-eyereflector 533, it is reflected by third right-eye reflector 534 andredirected onto right-eye diffuser 233.

A real-image created on left-eye diffuser 243 is transmitted to left-eye146 by left eyepiece optics 145. Left eyepiece 560 is made up of secondleft-eye reflector 543, third left-eye reflector 544, left-eye diffuser243, and left eyepiece optics 145, collectively. A real-image created onright-eye diffuser 233 is transmitted to right-eye 136 by right eyepieceoptics 135. Right eyepiece 561 is made up of second right-eye reflector533, third right-eye reflector 534, right-eye diffuser 233, and righteyepiece optics 135, collectively. Device 500 is capable of dioptercorrection through movement 153 of left eyepiece optics 145 and movement154 of right eyepiece optics 135.

Device 500 can adjust IPD 150 as depicted in FIG. 5B. In Device 500,left eyepiece 560 is rotatable about axis 541 with respect to left-eyereflector 142. When left eyepiece 560 rotates counter-clockwise aboutleft-eye reflector axis 541, optical sub-path 140 is deflected from itsprevious path by some angle phi (φ). Similarly, right eyepiece 561 isrotatable about axis 531 with respect to right-eye reflector 132. Whenright eyepiece 561 rotates clockwise about the right-eye reflector axis531, optical sub-path 130 is deflected some angle phi prime (φ′) fromits previous path. These deflections result in left eyepiece 560 andright eyepiece 561 rotating in the plane of the users face to adjustedIPD 550.

FIG. 6 illustrates a top view of a portion of a head mounted devicearranged according to an embodiment of the present invention. FIGS. 1-5have depicted embodiments using sub-image creation sections 101 and 401.However, embodiments are not limited to these arrangements. In FIG. 6,sub-image creation section 600 includes display 110 arranged normal todisplay axis 111. Display 110 projects a display image along opticalpath 112. A display image can then be focused by display lens 115 havinga lens focal point 124. Splitter 620 is a symmetric V-mirror splittercomposed of right fully reflective surface 622 and left fully reflectivesurface 621 that share a common edge and are arranged symmetricallyabout display axis 111. FIG. 6 has been depicted and described usingfully reflective surfaces, but such arrangements may be readily adaptedto the use of polarizing beam splitters or partially reflective surfacesas well. The arrangement of section 601 results in a display imageprojected by display 110 which is focused by display lens 115 and splitinto two display sub-images, one reflected along right-eye opticalsub-path 130 and one along left-eye optical sub-path 140.

Further optimization of the various embodiments of the present inventioncan be made by the use of collimated (or approximately collimated)light. A display that (approximately) produces, reflects, or isilluminated by collimated light can improve image quality and simplifiesdevice arrangement. There are numerous methods of producing andproviding collimated light to different aspects of HMD's, andembodiments are not limited to any one.

FIG. 7 illustrates a top view of a portion of a head mounted devicearranged according to the present invention. In sub-image creationsection 700, display 110 is arranged normal to display axis 111. Displaylens 115 is interposed between display 110 and splitter 620. Splitter620 is arranged as a symmetric V mirror splitter with fully reflectivesurface 621 and fully reflective surface 722. Focal point 124 of lens115 is proximate to splitter 620. Display 110 is illuminated by lightsources 708 and 709 which are reflected by source reflector 707, whichmay be a polarization splitter, or a partially reflective mirror, orother appropriate reflector. Sources 708 and 709 are arranged adjacentto display axis 111 and in a plane with reflected focal point 124R. Thesub-image created by source 708 and display 110 will be focused by lens115 and incident upon reflective surface 722 of splitter 620. Whendisplay 110 is illuminated by source 709, a separate display sub-imageis created and focused by lens 115. Because source 709 is positionedbelow reflected focal point 124R, the sub-image created by source 709and display 110 will be focused by lens 115 and incident upon reflectivesurface 621 of splitter 620.

In the embodiment of FIG. 7, two complete and independent images(referred to again as sub-images) of display 110 are created, and eachsub-image is a full image of display 110. In the embodiment of FIG. 7,splitter 620 does not split a single image to create sub-images, butrather splits the angular space of the display reflection allowing theindependently created images to be redirected along separate paths.

FIG. 8 illustrates a top view of a portion of a head mounted device 800arranged according to an embodiment of the present invention usingsub-image creation section 101. Blue source light 801 is arranged alongthe source light optical path 806, preferably in a position at or nearreflective focal point 124R of display optics 115. Blue source light 801may be any light source capable of producing blue light, such as NichiaNSC×100 series light emitting diode (LED). Light from blue source 801passes through a first color filter 804 arranged at an appropriate angleto the optical path and selected in order to pass blue light and toreflect green light. Green source 802 is placed adjacent to source lightoptical path 806 and arranged in order to reflect light off of firstcolor filter 804 in a way that simulates placing green source 802 in thesame location as blue source 801. Blue light and the reflected greenlight follow source light optical path 806 passing through second colorfilter 805 arranged at an appropriate angle to source light optical path806.

Second color filter 805 is selected such that it passes blue and greenlight, but reflects red light. Red source 803 is placed adjacent tosource light optical path 806 and arranged in order to reflect light ofsecond color filter 805 in a way that simulates placing red source 803in the same location as blue source 801. Blue light, reflected greenlight, and reflected red light then follows source light optical path806 and is reflected by source light reflector 807. In the depictedembodiment, source light reflector 807 can be a polarizing reflectorarranged about display axis 111 and along optical path 112. The combinedblue, green, and red light is polarized and reflected off of sourcelight reflector 807, through display optics 115. In the depictedembodiment, display optics 115 is a lens selected to have a focal pointof 124 (and a reflected focal point 124R). When passed through displayoptics 115, the combined blue, green, and red light is collimated andilluminates display 110. FIG. 8 depicts the illumination of display 110from a single direction, but the embodiments are not limited to a singledirection. Rather, the illumination system of FIG. 8 can be easilyadapted for multiple direction illumination as in FIG. 7.

The embodiments of the present invention are not limited to arrangementsthat place an image splitter proximate to the focal point of a focusingoptic. Rather, embodiments of the present invention are able to reducethe splitting volume of various applications, by positioning the imagesplitter to split a display image focused in a small area.

FIG. 9 illustrates the reduced splitting volume created by embodimentsof the present invention. In FIG. 9, display 110 is illuminated, thuscreating a display image. The display image propogates along opticalpath 112 arranged along display axis 111. Display lens 115, having adisplay lens focal point 124 a, focuses the display image in order toprovide a reduced splitting volume. The point where the splitting volumeis smallest will depend on the light illuminating the display.

When display 110 is illuminated by source 908 a positioned at reflectivedisplay lens focal point 924 a, display lens 115 will collimate thelight reflected from source reflector 707. This results in a displayimage that is focused by display lens 115 to approximately display lensfocal point 124 a. When display 110 is illuminated by source 908 bpositioned at point 924 b which is closer to display axis 111, the lightreflected from source 707 will be divergent as it strikes display 110.Thus, the display image will be focused to approximately point 124 c.When display 110 is illuminated by source 908 c, positioned at a point924 c which is farther away from display axis 111, the light reflectedfrom source reflector 707 will be convergent as it strikes display 110.Thus, the display image will be focused to approximately point 124 b.Embodiments of the present invention can thus be arranged to split thedisplay image at whichever point is most appropriate.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the invention asdefined by the appended claims. Moreover, the scope of the presentapplication is not intended to be limited to the particular embodimentsof the process, machine, manufacture, composition of matter, means,methods and steps described in the specification. As one will readilyappreciate from the disclosure, processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed that perform substantially the same function orachieve substantially the same result as the corresponding embodimentsdescribed herein may be utilized. Accordingly, the appended claims areintended to include within their scope such processes, machines,manufacture, compositions of matter, means, methods, or steps.

1.-35. (canceled)
 36. A system for channeling a displayed image, saidsystem comprising: a display that projects an image along an opticalpath; a lens that focuses the image; a splitter in proximity to the afocal point of said image for creating a plurality of displaysub-images, each said sub-image following one of a plurality of opticalsub-paths; eye-optics placed along said at least one optical sub-path;and means for forming a real-image arranged along said at least oneoptical sub-paths, arranged between said splitter and said eye-optics,and wherein a movement of said forming means maintains a constant lengthfor said optical sub-path.
 37. The system of claim 36 wherein saidmovement of said forming means may be used to adjust for inter pupillardistance.
 38. The system of claim 36 wherein said forming means is aspherical diffuser.
 39. The system of claim 36 wherein said formingmeans is a diffraction grating.
 40. The system of claim 36 wherein saidforming means is a microlens array. 41.-61. (canceled)
 62. The system ofclaim 36 wherein said movement of said forming means counteracts amovement of said eye-optics.
 63. A method of maintaining a constantoptical path length, said method comprising: generating a sub-image thatfollows an optical path through eye-optics to an eye of a user;arranging an optical element along said optical path before saideye-optics; and linking a movement of said optical element with amovement of said eye-optics, wherein said optical element movementcounteracts said eye-optics movement thereby maintaining said constantlength of said optical path.
 64. The method of claim 63 furthercomprising: orienting said eye-optics and said optical element atapproximately ninety degrees with respect to each other.
 65. The methodof claim 64 further comprising: arranging a beam splitter along saidoptical path, wherein said beam splitter passes at least a portion ofsaid sub-image to said optical element and reflects light from saidoptical element into said eye-optics.
 66. The method of claim 65 whereinsaid sub-image is reflected by said optical element.
 67. The method ofclaim 66 wherein a real image is created on said optical element. 68.The method of claim 63 wherein said eye-optics movement is a movementused to adjust a head mounted display for the interpupilar distance ofsaid user.
 69. A head mounted display, said display comprising: a firstoptical path; a first diffuser placed in said first optical path forminga first real image; a first eye-optics transmitting said first realimage to a first eye of a user; a first optical element placed in saidfirst optical path reflecting said first real image into said firsteye-optics; and first gearing means for linking movement of said firstoptical element and said first eye-optics; wherein said linked movementsaccommodate an interpupilar distance of a user while maintaining aconstant length for said first optical path.
 70. The head mounteddisplay of claim 69 wherein said first optical element alters said firstoptical path by approximately ninety degrees, and second optical elementalters said second optical path by approximately ninety degrees.
 71. Thehead mounted display of claim 69 wherein said first and second opticalelements are partially reflective surfaces arranged such that lightfollowing said first optical path passes through said first opticalelement to impact said first diffuser, and that light following saidsecond optical path passes through said second optical element to impactsaid second diffuser.
 72. The head mounted display of claim 69 whereinsaid first and second optical elements are polarizing beam splitters.73. The head mounted display of claim 69, further comprising: a secondoptical path; a second diffuser placed in said second optical pathforming a second real image; a second eye-optics transmitting saidsecond real image to a second eye of a user; a second optical elementplaced in said second optical path reflecting said second real imageinto said second eye-optics; and second gearing means for linkingmovement of said second optical element and said second eye-optics;wherein said second gearing means is capable of adjusting said headmounted display to an inter pupilar distance of a user and maintaining aconstant length for said first optical path.
 74. The head mounteddisplay of claim 73, wherein first and said second gearing means areindependent.